The flow of viscous, particle-laden wetting thin films on an inclined plane is studied experimentally as the particle concentration is increased to the maximum packing limit. The slurry is a non-neutrally buoyant mixture of silicone oil and either solid glass beads or glass bubbles. At low concentrations ͑ Ͻ 0.45͒, the elapsed time versus average front position scales with the exponent predicted by Huppert ͓Nature ͑London͒ 300, 427 ͑1982͔͒. At higher concentrations, the average front position still scales with the exponent predicted by Huppert on some time interval, but there are observable deviations due to internal motion of the particles. At the larger concentration values and at later times, the departure from Huppert is seen to strongly depend on total slurry volume V T , inclination angle ␣, density difference, and particle size range.